Over the years engine manufacturers have been working to improve the weight, size efficiency and manufacturing costs of engines. In part this has lead to the development of axial motors. An axial motor includes an engine block in which the cylinders are spaced evenly in a circular configuration about an axis of the engine block, rather than in the inline, “V” or horizontally opposed configurations of traditional engines. The reciprocal motion of the pistons in an axial motor can be transferred to rotational motion of an output shaft by way of a wobble plate configuration, such as that disclosed in NZ 221336.
Generally, as with conventional internal combustion engines, the compression ratio and therefore power output of the axial motor is at least in part limited by the quality of the fuel being burnt. If poor quality fuel is used, a lower compression ratio must be used in the motor or else “knocking” or auto-igniting will occur, which ultimately could damage components of the motor. Some higher density fuels (“heavy” fuels) such as diesel hydrocarbon fuel exhibit poor combustion properties as they are difficult to atomise prior to combustion, compared to lower density fuels (“light” fuels) such as petrol.
A number of internal combustion engines are configured to deliver exhaust gas under relatively low pressure to cylinders to go some way towards improving combustion properties and/or reducing emissions. Such engines are described in U.S. Pat. No. 6,427,644; U.S. Pat. No. 5,782,226; U.S. Pat. No. 4,475,524 and EP 0682743.
WO 03/008785 and WO 03/040530 to Scuderi describe four stroke split cycle internal combustion engines. The engines have a compression cylinder containing a compression piston and a power cylinder containing a power piston. The compression piston performs the intake and compression strokes of a four stroke cycle, and the power piston performs the power and exhaust strokes of the same four stroke cycle. A fresh air/fuel mixture is compressed in the compression cylinder and is delivered via a gas passage to the combustion cylinder for combustion, and then exhausted from the engine. The two pistons are provided so that the power piston can be offset to align the maximum combustion pressure with the maximum torque applied to the crank shaft, and so that the compression piston can be offset to align the maximum compression with the maximum torque applied from the crank shaft. The Scuderi systems do not address compression ratio issues. Only fresh compressed mixture is shared between cylinders.
It is an object of the present invention to provide a recirculation system for a motor which is operable to improve combustion properties and improve performance and/or which at least provides the public with a useful choice.